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    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p{
            position: fixed;
            width: 100%;
            background: red;
            top: 0;
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        body{
            height: 3000px;
        }
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</head>
<body>
    <!-- 定位 -->
    <p>信思智学</p>
    <span>hello snail</span>
</body>
</html>